The prior art provides many different article carrier designs. Initially, article carriers were rigidly mounted to the tops of vehicles. More recently, engineering developments have provided article carriers with movable crossbars which allow for adjustment when carrying articles of different sizes or configurations. However, the majority of these article carriers having movable crossbars or detachable crossbars are complicated or difficult to operate.
In general, the prior art provides article carriers comprising longitudinal side rails attached to a vehicle panel. One or two crossbars are provided having stanchions at opposite ends thereof to support the crossbars with respect to the longitudinal rails. The previous clamping mechanisms provided to clamp the stanchions with respect to the longitudinal side rails are generally complex and inconvenient to the operator.
U.S. Pat. No. 4,487,348 to Mareydt discloses an external cargo carrier for a vehicle, including a mechanism allowing longitudinal adjustment of a crossbar relative to a pair of transversely spaced side rails and permitting detachment of the crossbar from the side rails. The stanchion is provided with a jaw pivotally connected thereto and having a thumbwheel thereon for attachment to the stanchion. The stanchion is placed upon a lip of a longitudinal side rail, and the pivoting jaw is pivoted over the bottom of the lip in order to clamp onto the lip. The thumbwheel is then screwed in in order to tighten the jaw and stanchion over the lip. This design is somewhat impractical because it may be difficult to remove and reattach the pivoting jaw to the lip. The pivoting jaw is located beneath the stanchion in a difficult to reach area, and the thumbwheel is provided with a threaded screw for screwing into an internally threaded opening in the stanchion. Numerous turns of the thumbwheel are required in order to release or fully engage the clamp, particularly where a fine pitch is needed to reduce manipulation effort. This arrangement may be unduly difficult for the operator.
Another prior art design is disclosed in U.S. Pat. No. 4,270,681, which provides an article carrier with a slidable bracket. The rails include an open topped channel having a reduced access opening. The bracket includes a base section slidably movable in the channel that retains the bracket within the channel of the rail. The bracket and crossbar mounted to the bracket may be removed from the track only if the bracket is slid all the way to the open end of the farthest extent of the longitudinal rail. Moreover, the bracket can be locked into position along the longitudinal rail by a key which is threadably secured to a rotatable disk. As the disk is rotated, the key is urged into engagement with the base of a track to urge the base section of the bracket up against the top wall of the restricted channel opening in the longitudinal rail. Such a structure stresses the material forming the reduced opening for the channel in the longitudinal rail. Accordingly, this design is not desirable.
Other commonly known article carriers are disclosed in U.S. Pat. Nos. 4,162,755, 4,274,570 and 4,323,182. These patents disclose a stanchion element carried on top of a channeled longitudinal rail. The stanchion receives a through bolt carried by a locking plate that is retained within the rail channel. The bolt extends through the stanchion member for engagement with a rotatable wheel for tightening the bolt and pressing the top wall of the rail, including the restricted channel opening, between the plate and the stanchion element. However, the threaded bolt must be disengaged and removed from one of the threaded apertures in the wheel or the lower plate so that the parts may be separated for removal of the stanchion from the longitudinal rail. Alternatively, with the clamping device loosened, the stanchion and crossbar must be slid completely to one longitudinal end of the longitudinal rail to remove the stanchion and crossbar from the rack in the absence of complete disassembly of the bolt retaining mechanism.